I used multiple shades of blue in designing document, but now need to convert all blues to reflex blue for commercial printing. I will likely need to provide printer with just two separations: black and reflex blue. Please help me figure out how to do this as this is a first time job for what could turn out to be a good repeat customer. Thanks.

I presume you are going to have multiple tints of Reflex Blue, so you'll need to add Reflex Blue to the swatches, then create the tint swatches you will also need.

Second, you can only substitute one swatch for another if it is defined, so if you haven't already defined all of the colors in the file as swatches, open the Swatches panel flyout menu and choose Add Unnamed Colors to create a new swatch for every color used but not yet defined. You can then delete these one at a time or in groups (if they will all be replaced with the same tint) and choose the appropriate Reflex Blue swatch as Salah has outlined.